In regulations outlining the Affordable Care Act, the Treasury Department said employers with between 50 and 99 full-time workers won't have to comply with the law's requirement to provide insurance or pay a fee until 2016.

Companies with 100 workers or more could avoid penalties in 2015 if they showed they were offering coverage to at least 70% of their full-time workers, the Treasury said.

The move is a new, significant revision of the law after a series of delays and a troubled rollout. Originally, employers with the equivalent of 50 full-time workers or more had to offer coverage or pay a penalty starting at $2,000 per worker beginning in 2014.